Influence of cardiopulmonary bypass temperature on circulatory pathophysiology and clinical outcomes

This study was designed to investigate the effects of cardiopulmonary bypass (CPB) perfusion temperature. Forty-four patients who had undergone elective coronary bypass surgery were randomly divided into 2 groups (22 patients each) according to their perfusion temperature (N group = 36°C; L group = 30°C). The concentrations of endogenous catecholamines, complements, elastase, serotonin, arachidonic acid metabolites and endothelin underwent various changes throughout the CPB but did not exhibit any statistical differences in either group. None of the substances measured correlated with systemic vascular resistance at any time. The temperature of the perfusion appears to be a major determinant of vascular tone. The postoperative PO₂ was better, and postoperative pulmonary vascular resistance lower in the N group (p<0.05), most likely because of a much larger water balance during hypothermic CPB (p<0.01). The postoperative blood loss was statistically less in the N group (p<0.05). Although apparent brain damage, evidenced by the leakage of creatine kinase-BB, was not seen, the jugular bulb venous hemoglobin saturation levels (<50% in 27% of the N group, p<0.05) and higher lactate levels suggested that normothermic perfusion was relatively disadvantageous. It is concluded that normothermic CPB was relatively safe and advantageous with regard to hemostasis and pulmonary function.